Typical systems utilized to detect objects in or near the path of an elevator door employ an array of light sources disposed vertically on one edge of a door which provide light beams that energize a corresponding array of photodetectors disposed on an opposite edge of the door, whereby interruption of a light beam will cause a door open command to cause a door to become or remain open. Such systems are generally satisfactory but have the characteristic of not sensing things which are not within the discreet paths of light. Furthermore, with the light arrays being in a single plane, there is the opportunity to not sense the presence of persons or things until they have been extended some distance into the door opening.
More complicated elevator door obstruction detection is disclosed in U.S. Pat. Nos. 5,387,768 and 5,410,149. However, apparatus according to these disclosures sense only motion, and therefore do not sense objects which are static or immobile within the door pathway. Furthermore, the processing of images is highly complex and requires significant software and software processing time. The adaptation of such complex devices to elevator landings which have different image responses is also very complex, slow and expensive, due to the nature of the processing involved.
Current light beam door obstruction detectors require flexing cables to provide power to and receive responses from the moving doors.